1. Field of the Invention
The present invention relates to a navigation system making a route search from the current position to the destination or to transit points, and more particularly to a technology of finitely making a search according to a command for the propriety of use of special roads, such as, e.g., toll roads.
2. Description of the Related Art
Recently, the number of toll roads or toll special roads (hereinafter referred to as a “special road”) has been going on increasing, including fee-charging bridges and tunnels, toll bypass roads, expressways (FWY), toll reserved roads, and ferries. In the conventional on-vehicle navigation system, a method has been accounted for the mainstream, in which it sets the propriety of use (“use” or “non-use”) of special roads as a route condition before making a route search in a route search to the destination or to the transitpoints. In this case, e.g., when setting a condition that special roads are “used,” a calculation of the optimum route is made by taking all special roads to the destination into consideration, or, when setting a condition that special roads are “not used,” a calculation of the optimum route is made by not completely taking special roads to the destination into consideration.
In this connection, as a related art, Patent Document 1 discloses a navigation system which can present, by design, routes of a variety of toll fares to a user to increase the degree of freedom of user's route selection. In the navigation system, a searching section sequentially changes the cost of the toll roads to search for a plurality of potential candidate routes; a calculating section calculates a toll fare of each of the potential candidate routes searched by the searching section; the selecting section selects a plurality of routes of different toll fares from the plurality of searched candidate routes based on the result searched by the searching section and the result calculated by the calculating section; and a presenting section presents information on the plurality of routes selected by the selecting section.
Patent Document 1: JP-A2006-017507
In the conventional navigation system mentioned above, when the propriety of use of the special roads is set as a route condition, only specification of the use of all the special roads to the destination or the non-use of all the special roads is permitted. In general, a user has a propensity to select the use of the individual special roads by thinking about a charge for using the special roads or cost performance thereof, such as toll fares of the individual special roads to the destination or time efficiency thereof in limited conditions (for example, a user wants to use some of toll roads only in a commuting time period). Therefore, it has been hitherto on the tiptoe of expectancy of the development of a navigation system able to specify the propriety of use of the individual special roads.